July 3i, 1916 Life Cycles of the Bacteria 685 



per cent of all cases. During our first investigations upon this subject 

 (14) only 4 of 11 strains (No. 2, 4, 5, and 6) possessed this faculty, 

 which they had acquired between 1908 and 191 2. Culture 7 gave some 

 bodies looking like endospores in 1914, but they were not resistant to 

 heat. This faculty has now been fully developed. Cultures 15, 17, and 

 19, also typical spore-free cells at the time of their isolation some years 

 ago, showed their inclination to form endospores when first tested in this 

 direction in 191 5. Cultures 23 to 25 developed this special character dur- 

 ing the time we were experimenting with them. To fix exactly the con- 

 ditions for transforming a spore-free into a spore-bearing strain will 

 be one of the tasks in our later, detailed investigations. As already in- 

 dicated, a close study of the symplasm and of the regenerative bodies 

 derived from it will solve this problem as well as many others concerning 

 the multitude of forms inclosed in the life cycles of the bacteria. 



Unquestionably in all such experiments the inner condition of the 

 cells is of no little importance. That at least in some directions this 

 factor can eventually outmatch the influence of the outer conditions to 

 a considerable extent is clearly shown by the interesting behavior of 22 

 of our Azotobacter strains when they were inoculated into soil extract 

 containing 1 per cent of mannite and 0.05 per cent of monobasic potas- 

 sium phosphate (KH 2 P0 4 ), after having grown previously in moist 

 sterilized soil and mannite. Fifteen of these cultures grew in the large 

 types A and L and seven in the small types B and F when the experiment 

 started. Two weeks later, without a single exception, all the fifteen strains 

 changed from types A, B, and L to D, E, and F. Vice versa, the seven 

 others produced types D and I, these developing into types A, B, and L. 

 This result corroborates once more our statement that every strain of 

 Azotobacter or of any other bacillus will pass through all phases of its 

 cycle of life persistently if the conditions are suitable. Undoubtedly and 

 in full accordance with the behavior of higher organisms, some strains 

 are especially inclined to grow mostly in one or the other subcycle. 

 However, the formation of the symplasm and its "plasticity" enables 

 us, if we make use of these interesting possibilities, to induce and accelerate 

 changes in the general development of a bacillus to which the special 

 strain perhaps may be only very little inclined at that time. For ex- 

 ample, our five newly isolated Azotobacter cultures 21 to 25 had, of 

 course, the pronounced tendency to grow in their typical large globular 

 or oval form. Only in about 1 -month-old mannite solutions were the 

 long rodlike forms more numerous, mixed with forms belonging to types 

 A, B, D, E, F, and I. Transfers on mannite agar, after one day, gave in 

 four cases an abundant and practically pure growth of the large rods, 

 showing a tendency to form endospores. Only one culture (No. 24) 

 failed, because in this case we had no such old solution at hand and had 

 started, therefore, from a 3-day-old culture, which exclusively produced 

 round and oval regenerative bodies on mannite agar. 



